Reversal of bortezomib resistance in myelodysplastic syndrome cells by MAPK inhibitors

MEK/ERK and PI3K/AKT pathway inhibitors affect the transformation of myelodysplastic syndrome into acute myeloid leukemia via H3K27me3 methylases and de‑methylases

The transformation of myelodysplastic syndrome (MDS) into acute myeloid leukemia (AML) poses a significant clinical challenge. The trimethylation of H3 on lysine 27 (H3K27me3) methylase and de‑methylase pathway is involved in the regulation of MDS progression. The present study investigated the functional mechanisms of the MEK/ERK and PI3K/AKT pathways in the MDS‑to‑AML transformation. MDS‑AML mouse and SKM‑1 cell models were first established and this was followed by treatment with the MEK/ERK pathway inhibitor, U0126, the PI3K/AKT pathway inhibitor, Ly294002, or their combination. H3K27me3 methylase, enhancer of zeste homolog (EZH)1, EZH2, demethylase Jumonji domain‑containing protein‑3 (JMJD3) and ubiquitously transcribed tetratricopeptide repeat on chromosome X (UTX) and H3K27me3 protein levels were determined using western blot analysis. Cell viability, cycle distribution and proliferation were assessed using CCK‑8, flow cytometry, EdU and colony formation assays. The ERK and AKT phosphorylation levels in clinical samples and established models were determined, and SKM‑1 cell behaviors were assessed. The levels of H3K27me3 methylases and de‑methylases and distal‑less homeobox 5 (DLX5) were measured. The results revealed that the ERK and AKT phosphorylation levels were elevated in patients with MDS and MDS‑AML, and in mouse models. Treatment with U0126, a MEK/ERK pathway inhibitor, and Ly294002, a PI3K/AKT pathway inhibitor, effectively suppressed ERK and AKT phosphorylation in mice with MDS‑AML. It was observed that mice with MDS treated with U0126/Ly294002 exhibited reduced transformation to AML, delayed disease transformation and increased survival rates. Treatment of the SKM‑1 cells with U0126/Ly294002 led to a decrease in cell viability and proliferation, and to an increase in cell cycle arrest by suppressing ERK/PI3K phosphorylation. Moreover, treatment with U0126/Ly294002 downregulated EZH2/EZH1 expression, and upregulated JMJD3/UTX expression. The effects of U0126/Ly294002 were nullified when EZH2/EZH1 was overexpressed or when JMJD3/UTX was inhibited in the SKM‑1 cells. Treatment with U0126/Ly294002 also resulted in a decreased H3K27me3 protein level and H3K27me3 level in the DLX5 promoter region, leading to an increased DLX5 expression. Overall, the findings of the present study suggest that U0126/Ly294002 participates in MDS‑AML transformation by modulating the levels of H3K27me3 methylases and de‑methylases, and regulating DLX5 transcription and expression.

DAXX inhibits cancer stemness and epithelial-mesenchymal transition in gastric cancer

BACKGROUND

DAXX is a transcription repressor that has been implicated in several types of cancers, but its role in the development of gastric cancer remains unknown.

METHODS

We analysed the expression of DAXX in 83 pairs of gastric cancer samples, including neoplastic and adjacent tissues, and correlated the expression levels with clinical stages. We also investigated the molecular mechanisms by which DAXX downregulation promotes cancer growth using both in vitro and in vivo models.

RESULTS

DAXX was downregulated in advanced gastric cancer samples. The expression of DAXX inversely correlates with that of cancer stem cell markers CD44 and Oct4 in gastric cancer lines. DAXX overexpression in gastric cancer cells inhibited migration, invasion and epithelial- mesenchymal transition (EMT). The inhibition of EMT was achieved through the repression of SNAI3, a key inducer of EMT, by recruiting HDAC-1 into the nucleus. Using a xenograft mouse model, we demonstrated that the MKN45 cells formed smaller tumours when DAXX was overexpressed. Wild-type AGS cells were not able to form tumours in nude mice, but in contrast, formed visible tumours when DAXX was silenced in the cells.

CONCLUSION

We for the first time demonstrated that DAXX functions as a tumour suppressor in gastric cancer by inhibiting stem cell growth and EMT.

Retracted: EBF1 gene promotes the proliferation and inhibits the apoptosis of bone marrow CD34+ cells in patients with myelodysplastic syndrome through negative regulation of mitogen-activated protein kinase axis

The transcription factor, early B cell factor 1 (EBF1), plays a vital role in the lineage specification involving early B cell development and the onset of myelodysplastic syndrome (MDS). Therefore, to investigate whether or not EBF1 affects MDS as well as the transcription factor's underlying mechanism, we used CD34+ hematopoietic stem cells in bone marrow from patients with MDS. The extracted cells were then transfected with a series of EBF1, short hairpin RNA against EBF1 (shEBF1), and SB203580 (a specific mitogen-activated protein kinase [MAPK] axis inhibitor). The effects EBF1 gene and MAPK axis had on cell proliferation, apoptosis, and migration were determined by in vitro cell culturing. We made observations that involved EBF1 inhibiting the messenger RNA (mRNA) level of p38 MAPK, increasing the mRNA levels of extracellular-signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), extracellular-signal-regulated kinase 5 (ERK5), decreasing the protein expression of Bcl-2-associated X protein (Bax), and finally elevating the protein levels of B cell lymphoma/leukemia-2 (Bcl-2), stem cell factor (SCF), erythropoietin receptor (EpoR), p-ERK, p-JNK, p-ERK5, cyclin D, cyclin E, cyclin-dependent kinase 2 (CDK2), and CDK6, implying that EBF1 may very well have an inhibitory role in the MAPK axis. Another discovery found that EBF1 had a positive effect on the promotion of bone marrow CD34+ cell proliferation as well as its migration, but inhibited the apoptosis of cells. The results we obtained from this study indicated that the EBF1 gene suppresses the activation of the MAPK axis, thereby promoting both the proliferation and migration of bone marrow CD34+ cells as well as inhibiting the associating apoptosis. The effects of the EBF1 gene are likely to present a new therapeutic target in preventing the progression of MDS.

GEP analysis validates high risk MDS and acute myeloid leukemia post MDS mice models and highlights novel dysregulated pathways

Background

In spite of the recent discovery of genetic mutations in most myelodysplasic (MDS) patients, the pathophysiology of these disorders still remains poorly understood, and only few in vivo models are available to help unravel the disease.

Methods

We performed global specific gene expression profiling and functional pathway analysis in purified Sca1+ cells of two MDS transgenic mouse models that mimic human high-risk MDS (HR-MDS) and acute myeloid leukemia (AML) post MDS, with NRASD12 and BCL2 transgenes under the control of different promoters _MRP8NRASD12/_tethBCL-2 or _MRP8[NRASD12/hBCL-2], respectively.

Results

Analysis of dysregulated genes that were unique to the diseased HR-MDS and AML post MDS mice and not their founder mice pointed first to pathways that had previously been reported in MDS patients, including DNA replication/damage/repair, cell cycle, apoptosis, immune responses, and canonical Wnt pathways, further validating these models at the gene expression level. Interestingly, pathways not previously reported in MDS were discovered. These included dysregulated genes of noncanonical Wnt pathways and energy and lipid metabolisms. These dysregulated genes were not only confirmed in a different independent set of BM and spleen Sca1+ cells from the MDS mice but also in MDS CD34+ BM patient samples.

Conclusions

These two MDS models may thus provide useful preclinical models to target pathways previously identified in MDS patients and to unravel novel pathways highlighted by this study.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0235-8) contains supplementary material, which is available to authorized users.